Automatic replenisher for the hydro-pneumatic recoil systems of large caliber guns

ABSTRACT

In order to maintain a uniform starting point for the reciprocable piston in a hydropneumatic recuperator of the type utilized in the recoil systems of large caliber guns, a reservoir is jointly connected to each of the gas and oil chambers in the recuperator and is provided with a floating piston arranged to separate the oil and the gas into individual areas and maintain an equilibrium position therebetween arranged to return the recuperator piston against a fixed stop at the end of each firing cycle regardless of any change in the volume of the oil.

United States Patent Inventors Robert E. Seamands Moline, 111.; Elmer J.Ilenning, Bettendorf, Iowa Appl. No. 878,121 Filed Nov. 19, 1969Patented Aug. 17,1971 Assignee The United States of America asrepresented by the Secretary of the Army AUTOMATIC REPLENISI-IER FOR THEHYDRO- PNEUMA'IIC RECOIL SYSTEMS 0F LARGE CALIBER GUNS [56] ReferencesCited UNITED STATES PATENTS 3,410,174 11/1968 l-lahn 89/43 PrimaryExaminer-Benjamin A. Borchelt Assistant Examiner-Stephen C. BentleyAttorneys-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and AlbertE. Arnold, .l r.

ABSTRACT: In order to maintain a uniform starting point for thereciprocable piston in a hydropneumatic recuperator of the type utilizedin the recoil systems of large caliber guns, a reservoir is jointlyconnected to each of the gas and oil chambers in the recuperator and isprovided with a floating piston 4 Gamma Drawing Flgs' arranged toseparate the oil and the gas into individual areas US. Cl 89/43 R andmaintain an equilibrium position therebetween arranged Int. Cl. F41f19/02 to return the recuperator piston against a fixed stop at the endField of Search 89/42 R, 42 of each firing cycle regardless of anychange in the volume of A, 42 B, 43 R, 43 A, 44 the oil.

I 34 717/4 on. I l g g 5 36 4 0 g 0| L G A 5 g E 54 64 s \l 11:! 72 F E42 58 6O 62 52 48 5s 5 s; 5 E l 1 l\ J AUTOMATIC REPLENISHER FOR THEHYDRO- PNEUMATIC RECOIL SYSTEMS OF LARGE CALIBER GUNS BACKGROUND OF THEINVENTION The present invention relates to hydropneumatic recoil systemsfor artillery weapons and is more particularly directed to means forinsuring relative uniformity to each return of the recoiling parts tobattery position despite any change in the volume of the hydraulic oilin the recoil system.

In current recoil systems for artillery weapons of relatively largecaliber, the flow of the hydraulic oil from the recoil cylinder to therecuperator during the recoil phase of the firing cycle is customarilyutilized to actuate a floating piston in the recuperator for compressinga quantity of nitrogen gas therein to furnish the motive power for thesubsequent return of the recoiling parts to battery position. Therequired oil flow is, in turn, achieved by the displacement of a pistonhead slidably seated in the recoil cylinder with a stem extendingexteriorly thereof into fixed engagement with the recoiling parts. Inorder to ensure substantially equal trunnion forces from one firingcycle to the next, the floating piston in the recuperator must bereturned to essentially the same starting point at the conclusion ofeach firing cycle. Such require'ment'can be simply achieved by theprovision of a fixed stop within the interior of the recuperator in thecounterrecoil path of the floating piston. However, since the heatgenerated in the recoil system during the relatively sustained firingfrequently required in modern warfare generally produces anunpredictable increase in the volume of the hydraulic oil therein,considerable difficulty has been encountered in maintaining the desireduniformity in the starting point of the floating piston.

It has been suggested, therefore, that a spring-operated member beslidably interposed between the head of the floating piston and thenitrogen gas to accommodate the expanded volume of the hydraulic oilwithout disturbing the required abutment between the piston head and thefixed stop in the recuperator. However, this expedient has not provensatisfactory inasmuch as the expansion of the oil frequently reachessuch proportions that the slidable member carries the spring entirelyout of contact with the piston head thereby eliminating the restraintnecessary to maintain the latter against the fixed stop. While the biasof the spring could be increased sufficiently to cope with theanticipated change in the volume of the oil, the resulting increase inthe size and weight thereof would be prohibitive.

' Accordingly, it is an object of this invention to provide ahydropneumatic recoil mechanism in which the hydraulic oil isautomatically maintained at a relatively constant pressure despite anyleakage or heat expansion thereof.

A further object of this invention is to provide a replenisher unit forthe aforesaid recoil mechanism which will operate to return the floatingpiston in the recuperator to the same starting position at the end ofeach firing cycle regardless of changes in the volume of the oiltherein.

Still another object of the present invention lies in the provision of areplenisher unit as aforesaid which will automatically compensate forany loss or gain in the volume of the oil without the need for amechanical spring.

SUMMARY OF THE INVENTION It has been found that these objects can bestbe attained by adding a replenisher unit to the recuperator in the formof a cylindrical reservoir in respective communication with both the oiland gas portions thereof and providing a slidable piston in thereservoir to separate the oil from the gas. The gas side of thereservoir piston is formed with a rod extending outwardly through thecorresponding end of the cylinder to serve as an indicator for anychange in the volume of the oil in the entire recoil mechanism. Theresulting reduction in the reservoir piston area exposed for contact bythe nitrogen gas results in a differential pressure which, under staticconditions, will permit the reservoir piston to compensate for changesin the volume of the oil while the initial higher pressure of the gascontinues to maintain the recuperator piston against the fixed stop.Thus, in the event of an increase in the volume of the oil, thecorresponding increase in the pressure thereof will actuate thereservoir piston to a new equilibrium position without changing theposition of the recuperator piston. Such is also the case in the eventof any decrease in oil inasmuch as the compressed nitrogen gas willdisplace the reservoir piston until equilibrium is again attained. Theoil passage between the recuperator and the reservoir is restricted tosuch extent that oil will not flow therethrough during the actuation ofthe recoiling parts.

BRIEF DESCRIPTION OF THE DRAWINGS The exact nature of the invention aswell as other objects and advantages thereof will be readily apparentfrom consideration of the following specification relating to theannexed drawings wherein:

FIG. 1 is a schematic sectional representation of a hydropneumaticrecoil unit for a gun of large caliber, such unit being secured to theunderside of the stationary cradle in which the carrier for the gun tubeis slidably mounted and shown in the battery position thereof;

FIG. 2 is a view similar to that of FIG. 1 but showing the relationshipof the parts during the initial portion of the recoil cycle; and

FIG. 3 is a fragmentary schematic sectional representation showing therecuperator piston at the conclusion of a firing cycle and the differentpositions of the reservoir piston at such point, the latter being shownin full in the position required to compensate for an increase in thevolume of the oil and shown in phantom in the position required tocompensate for a decrease in the volume of oil.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring more particularly to thedrawings wherein similar reference characters have been employed todesignate corresponding parts throughout, there is shown a large calibergun tube 12 to which a suitable carrier 14 is fixedly secured as byrings or loops 16. Carrier 14 is, in turn, slidably mounted in alongitudinal track 18 within the interior of a stationary cradle 20.Fixedly mounted to cradle 20 is a recoil unit 22 which, for simplicityof explanation, is here schematically illustrated and consequently doesnot show the actual size and relative position of the various componentsthereof. However, it should be understood that the forward and rearwardends of recoil unit 22 are oriented in the same respective directions asthe muzzle and breech ends of gun tube 12.

Recoil unit 22 includes a recoil cylinder 24 suitably fastened to cradle20 and a piston 26 slidably disposed in cylinder 24. Piston 26 isprovided with a rod 28 which extends through the rearward end wall ofcylinder 24 into fixed engagement with a depending portion 30 of carrier1 4 he portion of cylinder 24 through which rod 28 passes is utilized tohouse a quantity of hydraulic fluid, such as recoil oil, ad piston 26 istherefore provided with a suitable seal 32 arranged for slidable contactwith the interior wall surface of cylinder 24. The forward end v il ofcylinder 24 is provided with an opening or outlet 3. therethrough topermit exhaustion of the air therefrom during the counterrecoil strokeof piston 26.

A recuperator 36 preferably formed with a cylindrical housing 38 isconnected to recoil cylinder 24 to form an oil passage 40 therebetweenin the vicinity of the rear end wall thereof.

' Within housing 38 and in spaced relation to the interior wallincreasing depth. The rear end of tubular member 42 is spaced forwardlyof the corresponding end wall of housing 38 to open into the vicinity ofoil passage 40. A barrier wall 48 with a central hole 50 therethrough isformed within housing 38 in spaced relation to the front end of flangeportion 44 to form an accumulation chamber 52 for the oil flowingthrough tubular member 42. Forwardly of wall 48, the interior wallsurface of housing 38 is provided with oppositely disposed lugs or stops54 which serve to establish the starting point for the reciprocatingtravel of a piston 56 provided with a longitudinally extending controlrod 58 slidably engageable in tubular member 42.

A plurality of throttling slots 60 of progressively increasing depth arecircumferentially spaced about the exterior periphery of control rod 58and extend from the rear end thereof to a length which will terminateslightly forwardly of barrier wall 48 when the rear end of piston 56 isin abutment with stops 54. Forwardly of the head of piston 56, housing38 is filled with nitrogen gas which is arranged to be compressed bypiston 56 during the forward stroke thereof in order to pro vide themotive power required to return the recoiling parts of the gun to thebattery position thereof. A check valve 62 is contained in flangeportion 44 to permit oil to flow into accumulation chamber 52 during theforward movement of piston 56 and yet operate to block any flowtherethrough during the return movement of piston 56.

Suitable ducts 64 and 66 extending from opposite end portion ofrecuperator 36 provide for the coextensive connection thereto of agenerally cylindrical replenisher 68. Duct 64 is formed with arestricted opening 70 therein which effectively prevents any surging ofthe oil therethrough during the movement of control rod 58 and yet, oncesuch rod comes to a halt, permits oil to flow between recuperator 36 andreplenisher 68 in the event of any change in the volume of the oil. Duct66, on the other hand, is of sufficient diameter to permit ready passageof the nitrogen gas therethrough in either direction responsive to themovement of piston 72 slidably seated in replenisher 68 in sealingengagement with the interior wall surfaces thereof. Piston 72 is alsoprovided with a forwardly extending rod 74 projecting out through thefront end wall of replenisher 68 and provided with spaced indicia 76arranged to indicate the quantity of oil within the entire system. Oneof the indicia is specifically located and marked, as at 78, so as to bepositioned slightly beyond the forward end wall of replenisher 68 in theabsence of any increase or decrease in the volume of the oil. Thedifferential area formed by the opposite faces of replenisher piston 72is such that the pressure of the gas thereon is at all times slightlygreater than the pressure of the oil.

During the recoil movement of gun tube carrier 14 in cradle 20, piston26 is pulled along therewith to force oil from recoil cylinder 24 intorecuperator 36. The force thus applied against the rear end of controlrod 58 displaces piston 56 out of contact with stops 54. As control rod58 moves forwardly, throttling slots 60 therein and throttling grooves46 in the tubular member 42 are both exposed for the passage of oiltherethrough. At the same time, the flow of oil into recuperator 36opens check valve 62 to increase the quantity which will pass throughaccumulation chamber 52 and act against the rear face of the head onpiston 56 to continue the forward movement thereof. Piston 56 continuesforwardly until the recoil forces produced by the firing of the gun areabsorbed by the combination of the frictional forces opposing suchtravel, the pressure drop in throttling grooves 46, and the increasingcompression of the nitrogen gas. As the gas is thus compressed, piston72 in replenisher 68 remains virtually stationary since it is isolatedfrom transient conditions in the pressure ofthe oil by restrictedopening 70 in duct 64.

During the counterrecoil or return travel of control rod 58, thecompressed nitrogen gas in recuperator 36 actuates piston 56 to forceoil back into recoil cylinder 24 and thereby operate piston 26 to returncarrier 14 to the battery position in cradle 20. As oil begins to flowrearwardly through accumulation chamber 52, check valve 62 is closed tolimit the flow of oil to the space between control rod 58 and tubularmember 42. Since throttling grooves 46 and slots 60 decrease in depth ina rearward direction, the resulting resistance to the rearward travel ofcontrol rod 58 prevents excessive impact of carrier 14 against themating portion of cradle 20. In the event the oil in the system expandsdue to the heat engendered therein by any relatively sustained firingoperation of the gun and thereby prevents control rod piston 56 fromreaching stops 54 once the recoiling parts have attained batteryposition, the resulting imbalance of the forces on replenisher piston 72will automatically adjust the latter to permit the excess oil in therecuperator 36 to flow therefrom into replenisher 68 through restrictedopening 70. Thus, recuperator piston 56 will return to its startingposition in contact with stops 54. In the event any leakage of the oilor any substantial drop in the temperature thereof produces a decreasein volume which will permit control rod piston 56 to reach stops 54before the recoiling parts attain battery position, the imbalance of theforces on replenisher piston 72 will automatically move the latterrearwardly, as best indicated in FIG. 3, to force additional oil throughrestricted opening 70 into recuperator 36 to restore the volumeoriginally contained therein and in recoil cylinder 24.

Thus, there is here provided improved means for compensating for anyloss or gain in the volume of the oil in a combined recoil andrecuperator system in order to ensure the return of the recuperatorpiston to the same starting position for each firing cycle. The use of afloating piston in an added replenisher separately connected to each ofthe oil and gas portions of the recuperator is a simple yet positiveexpedient for maintaining the required equilibrium between the oil andgas pressures at the beginning of each firing cycle.

We wish it to be understood that we do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

We claim:

1. In a large caliber gun having a hydropneumatic recoil mechanismincluding a recuperator unit with a reciprocating piston responsive tothe recoil fiow of oil thereagainst for compressing a quantity ofnitrogen gas to provide the motive power for returning the recoilingparts of the gun to battery position, means for returning therecuperator piston to the same starting position at the end of eachfiring cycle comprising,

a replenisher connected to each end of the recuperator, and

a piston slidably seated in said replenisher between the oil and the gastherein to maintain an equilibrium position responsive to changes in thequantity of oil within the entire recoil mechanism.

2. The invention defined in claim 1 wherein said replenisher piston iscontoured to produce a differential pressure thereon responsive tochanges in the volume of the oil in the recoil mechanism.

3. The invention defined in claim 1 wherein said replenisher pistoncomprises a head and a rod extending from one s de of said head throughthe nitrogen gas to project outwardly of said replenisher whereby thearea exposed to the oil is larger th; the area exposed to the gas toprovide a differential pressure thereagainst for normally urging saidpiston to compensate for changes in the volume of oil.

4. The invention defined in claim 1 wherein the conn ction between therecuperator and said replenisher includes a restricted passage forpreventing the flow of oil therebetween during the reciprocation of therecoiling parts without affecting the required equalization of thepressure between the oil in the recuperator and the oil in saidreplenisher following the termination of the counterrecoil movement ofthe recoiling parts.

1. In a large caliber gun having a hydropneumatic recoil mechanismincluding a recuperator unit with a reciprocating piston responsive tothe recoil flow of oil thereagainst for compressing a quantity ofnitrogen gas to provide the motive power for returning the recoilingparts of the gun to battery position, means for returning therecuperator piston to the same starting position at the end of eachfiring cycle comprising, a replenisher connected to each end of therecuperator, and a piston slidably seated in said replenisher betweenthe oil and the gas therein to maintain an equilibrium positionresponsive to changes in the quantity of oil within the entire recoilmechanism.
 2. The invention defined in claim 1 wherein said replenisherpiston is contoured to produce a differential pressure thereonresponsive to changes in the volume of the oil in the recoil mechanism.3. The invention defined in claim 1 wherein said replenisher pistoncomprises a head and a rod extending from one side of said head throughthe nitrogen gas to project outwardly of said replenisher whereby thearea exposed to the oil is larger than the area exposed to the gas toprovide a differential pressure thereagainst for normally urging saidpiston to compensate for changes in the volume of oil.
 4. The inventiondefined in claim 1 wherein the connection between the recuperator andsaid replenisher includes a restricted passage for preventing the flowof oil therebetween during the reciprocation of the recoiling partswithout affecting the required equalization of the pressure between theoil in the recuperator and the oil in said replenisher following thetermination of the counterrecoil movement of the recoiling parts.